Valves have been the subject of engineering design efforts for many years, and millions of them have been used. The engineering development of valves has stagnated in this crowded and mature field of technology. Improvements have been elusive in recent years, even as the cost of materials and manufacturing has continued to climb.
The basic valve structure is present in several U.S. patent publications. Some of these describe conventional methods of building a valve, and others describe methods that have been rejected by industry. Fewer disclosures teach multiple component valves, as valves having multiple components have heretofore been disfavored for a number of reasons. Primarily, they are viewed as more costly to manufacture. Multiple components require multiple manufacturing steps, assembly steps, and fit-tolerances requirements that valves having fewer parts do not have. Secondly, each assembly and connection is deemed a potential failure point, so these valves are again, disfavored.
Fracking valves are a particular valve used to pump hard material into a production wellbore for the purpose of fracturing the reservoir containing formations to increase fluid flow into the wellbore. Such pumps are reciprocating, positive displacement pumps in which the valves are held closed by springs and open and close by differential pressure. The pumps deliver clear fluids or slurries through simple poppet valves that are activated (opened and closed) by the fluid pressure differential generated when the mechanical energy of the pump is converted into fluid pressure.
In oil and gas exploration, there are two common reciprocating, positive displacement applications; mud pumps and well service pumps. This invention is also appropriate in both of these categories as well as other, general industrial reciprocating, positive displacement applications. Pump valves in these applications must be guided as they move back and forth about an axis parallel to the fluid flow. The guides may be “stems” or “wings” and these may be on either side or both sides of the valve. They must remain an inseparable part of the pump valve during its useful life.
Due to the hardness of the material being pumped, valves include a soft seating material, such as a urethane insert, such that a seal can be obtained that would be prevented with a metal-to-metal valve seating. The softer insert component necessitates at least some assembly in frack valves. Other than the inclusion of the insert, conventional manufacturing practice has been to minimize the number of components in a valve assembly.
Conventional pump valves are thus made from a pair of near net shape pieces of low carbon alloy steel that are welded together and then carburized to produce a hard, wear resistant surface. The process of manufacturing such near net shapes is expensive. Alternatively, pump valves are made from high carbon, low alloy steels of one expensive piece that requires detailed finishing, as these alloys are generally not welded.
One form of convention valve manufacturing includes making the components of the valve of high alloy steel such as 8620 or 4130. These are expensive grades of steel for manufacturing a limited life product. Additionally, conventional manufacturing techniques generate waste.
Conventional valve guides are manufactured by investment casting. It is common practice to forge a one-piece valve and top stem of low carbon alloy steel. The two pieces are welded together and carburized as a single piece.
An alternative known method of making valves is to make a single investment casting of the entire valve for assembly with only the insert. As with the other method, the entire part is then carburized to harden it.
An alternative known method of making valves is to make a single piece forging from a high carbon alloy steel. Areas that require hardened surfaces are induction or flame hardened. However, the only areas of the valve that require hardened surfaces are relatively small and include the face of the valve and the outer edges of the guides.
The present invention replaces expensive raw material forms with a combination of inexpensive pieces and allows the most productive selective hardening processes to be used.